COMMUNITY FORUM

220 wire on a air compressor

Iam adding a air compressor to a 220 circut on my breaker panel.The guy at the store sold me 12-3 wire, I have a 3 prong 220 outlet what wire do I connect to the outlet ground [The bare ground wire or the white nuetral wire?], and do I put a wire nut on the wire that is not used?